<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
     /*  
     750    375
     100     50
      40     20
     */
    html{font-size:5.3333vw}
    .pic{
       width: 7.5rem;
       height:5rem
    }
    </style>
</head>
<body>
    <!-- 设计稿   750 *  1334 (>1334 多屏 滚动条) 
   容器: 300px   *  200px   图片
         150    *   100

      750       375          DPR
      100       50px         2.0

    -->

    <!-- 1rem = 100px  -->
    <div class="pic"></div>
    
</body>
</html>